Field of the Invention
The present invention relates to a brightness enhancement film, a polarizing plate comprising the brightness enhancement film, and an image display device.
Discussion of the Background
Image display devices such as liquid crystal display devices (also referred to as “LCDs” hereinafter) normally comprise at least an image display element such as a liquid crystal cell and a backlight unit.
As the energy consumption of backlight units has been reduced, it has been proposed that an optical sheet capable of enhancing brightness (the degree of brightness per unit area) be disposed between the backlight unit and the image display element to increase the rate of use of the light emitted by the light source contained in the backlight unit. Such an optical sheet is called a brightness enhancement film. The brightness enhancement film is expected to become core parts of low power image display devices as mobile devices increase in number and the power consumption of household appliance products decreases.
An optical sheet, commonly called a prism sheet, in the surface of which is formed a concavo-convex shape through which light that has entered through a backlight unit exits, has been proposed as a brightness enhancement film (for example, see Japanese Unexamined Patent Publication (KOKAI) Heisei No. 8-190806, which is expressly incorporated herein by reference in its entirety). Such prism sheets are available in the form of commercial products.